1. Technical Field
The present disclosure relates to a liquid pump and a rankine cycle apparatus including the liquid pump.
2. Description of the Related Art
Energy systems that use natural energy sources such as sunlight or exhaust heat have attracted attention recently. One example of such energy systems is a rankine cycle system. In a typical rankine cycle system, an expander is activated by a high-temperature and high-pressure working fluid to generate electricity. The high-temperature and high-pressure working fluid is generated by a pump and a heat source (solar heat, geothermal heat, and exhaust heat from automobiles, for example). Thus, a liquid pump is used in the rankine cycle system.
As illustrated in FIG. 7, Japanese Patent No. 2977228 describes a canned refrigerant pump 300. The canned refrigerant pump 300 includes a scroll pump 320 as a positive displacement pump mechanism. The scroll pump 320 includes a fixed scroll 321 and an orbiting scroll 322. Rotational movement of the orbiting scroll 322 allows a refrigerant to be drawn through a suction pipe 333 and ejected into an ejection chamber 329. Some of the refrigerant in the ejection chamber 329 flows through a first groove 348 or a second groove 349 as a lubricating refrigerant. As a result, a thrust bearing 330a and a surface of a bearing 309a are lubricated. Then, the refrigerant further flows into a space 343a. A major part of the refrigerant in the ejection chamber 329 flows into the space 343a, which is defined by a sealed case 306, through a through hole 338, a back pressure chamber 337, and a case communication hole 344. Then, the refrigerant in the space 343a flows into a space 343b through a passage 345 or a communication groove 350. The refrigerant in the space 343b is expelled through a discharge pipe 347.
As illustrated in FIG. 8, Japanese Unexamined Patent Application Publication No. 2001-41175 describes a liquid refrigerant pump 500. The liquid refrigerant pump 500 includes a sealed container 501, an electrical motor 502, and a positive displacement pump mechanism 503. The electrical motor 502 and the positive displacement pump mechanism 503 are disposed in the sealed container 501. The positive displacement pump mechanism 503 includes a crankshaft 504, a rolling piston 506, and a cylinder block 570 fixed to the sealed container 501. Rotary drive of the crankshaft 504 by the electrical motor 502 allows a liquid refrigerant to be drawn to the positive displacement pump mechanism 503 through a suction pipe 520 and an inlet 521 and allows the liquid refrigerant in a compressor 514 in the positive displacement pump mechanism 503 to be expelled through an outlet 523 and a discharge pipe 522. In the liquid refrigerant pump 500, the liquid refrigerant in the compressor 514 in the cylinder block 570 leaks to outside the cylinder block 570 through a groove 551. The leaked liquid refrigerant is mixed into a liquid refrigerant E stored in the sealed container 501 as a lubricant.